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National Electrical Code Articles and Information

NEC Quiz: Article 388 Answers

by Mark Lamendola

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  1. This wiring method is the nonmetallic counterpart to the surface metal raceway covered in Article 386. It's a nonmetallic raceway that's supposed to be mounted to the surface of a structure [388.2]. And the requirements for nonmetallic are very similar to those for metallic. An obvious issue is that metallic raceway is conductive and nonmetallic is not; this has implications for bonding requirements and for static control (e.g., use in hazardous locations). Generally, this raceway has very high aesthetic value. It's meant to be installed as a system, using the couplings, connectors, boxes, and fittings for that particular system.

  2. There are two permitted uses (the metallic version has four). The two are: In dry locations and extending through walls and floors (this last one has conditions for permissibility) [388.10]. What is different: The metallic version can also be used in Class I, Division 2 hazardous locations as permitted in 501.10(B)(3) and under raised floors, as permitted in 645.29(1),

  3. There are actually seven uses not permitted. For metallic, there are five.

    What is different: For nonmetallic, one of the two permitted uses missing from the list of four for metallic is moved to the not permitted list for nonmetallic and made more general . It is: in hazardous locations (except as as permitted elsewhere in the NEC). Nothing is said about "under raised floors," so if they are a dry location the NEC permits installation there.

    Plus other five listed for the metallic version (Article 386): Where subject to severe damage; where subject to corrosive vapors; where the voltage between conductors is 300V or more (unless specific special circumstances exist); in hoistways; where concealed (except as permitted in 388.10(2)) [388.12]. Plus one more restriction: For conductors whos insulation temperature would exceed those for which the nonmetallic raceway is listed. This restriction does not explicitly appear in Article 386, but common sense tells us it's there anyhow.

  4. Secure the raceway per the manufacturer's installation instructions [388.30]. Note that deviating from these instructions may well produce an installation that violates the listing of the components. They are meant to be assembled and supported in specific ways, and they are tested with those assembly and support means to get their testing lab listing.
  5. You can use only listed components [388.6]. Maybe something you'd normally use for EMT would handily solve an installation problem, but using it would render the installation out of compliance with the Code. You can't "field-design" these systems. If you do run into an intractible problem, most manufacturers have outstanding technical support and they can usually provide a ready solution. If they can't, then you need to come up with some other code-compliant solution (e.g., run that problem section of the circuit in EMT, to a box, then come back out to the surface raceway) or get special permission from the AHJ.



How the NEC is arranged

  1. The first four Chapters of the NEC apply to all installations.
  2. Article 90 precedes Chapter One, and establishes the authority of the NEC.
  3. Article 80 follows the body of the NEC; it exists as Annex H. It provides the requirements for administration.
  4. Chapters 5, 6, and 7 are the "special" chapters, covering special: occupancies, equipment, and conditions (in that order).
  5. Chapter 8 provides the requirements for communications systems.
  6. Chapter 9 provides tables.
  7. The appendices provide mostly reference information.
  8. Appendix D contains examples that every NEC user should study.

Try your NEC moxy:

  • Do you know the difference between bonding and grounding? Hint: Look in the NEC, Article 100.
  • Does the NEC refer to grounding incorrectly in any of its articles? Yes! So be careful to apply the Article 100 definitions. Don't ground where you should bond.
  • When doing motor load calculations, which Article covers hermetic motors? Answer: While Article 440 covers the application of hermetic motors, it does so only by amending Article 430 because hermetic motors are a special case of motors. For motor load calculations, refer to Article 430.
  • Does the NEC provide a voltage drop requirement? Yes! It does so in a special case, which is Article 648 Sensitive Electronic Equipment. But for general applications, it does not provide a requirement; it merely provides a recommendation in a couple of FPNs.
  • Take our Code Quizzes.

Remember other applicable codes, rules, standards, and references:

  • OSHA's electrical worker safety rules.
  • IEEE standards.
  • NETA standards.
  • NFPA standards.
  • International Codes (if applicable to the installation).
  • State Codes (if the state has them).
  • Local ordinances and permit requirements.
  • Local fire codes.
  • Manufacturer requirements or guidelines.
  • Customer security requirements.
  • Industry standards.
  • Your company's own internal standards, practices, and procedures.
  • Engineering drawing notes.



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